1. Field of the Invention
The present invention relates to an apparatus for electronically controllable transmission, and more particularly, to an apparatus for electronically controllable transmission, the apparatus capable of shifting gears by sensing the magnetic flux density of a magnet as the magnet connected to a shift lever moves.
2. Description of the Related Art
Vehicle transmissions change gear ratios to maintain the torque of an engine constant according to the speed of a vehicle. To change the gear ratios of a transmission, a shift lever of the transmission may be operated. Generally, there are two types of transmissions. One is a manual mode transmission that allows a user to manually shift gears, and the other is an automatic mode transmission that automatically shifts gears according to the speed of a vehicle when a user selects a drive (D) mode.
Another type is a sports mode transmission that can operate both in a manual transmission mode and an automatic transmission mode. The sports mode transmission basically operates in the automatic transmission mode but switches to the manual transmission mode when a user selects a higher or lower gear. The sports mode transmission may also be configured by installing an automatic mode transmission next to a manual mode transmission.
Examples of gears that can be selected by a user in an electronic transmission include park (P), reverse (R), neutral (N), drive (D), and “+” and “−” in which an engine brake is operated. An electronic transmission includes a two-dimensional (2D) sensor, such as a linear hall sensor or a switch hall sensor, to sense the position of a shift lever. Here, the hall sensor is a sensor that uses a magnet and converts a magnetic force into an electrical signal. Thus, a gear selected by a user is sensed based on the electrical signal output from the hall sensor. Specifically, the position of the shift lever can be identified based on an electrical signal (mostly, a voltage) output from the hall sensor.
To sense the position of a shift lever moving in a forward or backward direction or in a lateral direction, that is, to sense shift positions (P, R, N and D) and select positions (+ and −) of the shift lever, a magnet connected to the shift lever is placed above a 2D hall sensor. The 2D hall sensor senses the magnetic flux density of the magnet as the position of the magnet changes in accordance with the movement of the shift lever.
However, the conventional 2D hall sensor requires a plurality of sensors for each gear and must maintain a constant gap between itself and the magnet. That is, the conventional 2D hall sensor requires an additional structure, such as a bracket, to move the magnet parallel to the 2D hall sensor, so that the gap between the 2D hall sensor and the magnet is maintained unchanged while the shift lever moves in the forward or backward direction or the lateral direction, thereby maintaining the intensity of the magnetic flux density of the magnet constant.
FIG. 1 is a perspective view of a conventional apparatus 20 for electronically controllable transmission. Referring to FIG. 1, in the conventional apparatus 20, an inner case 10 is inserted into a first holder unit 12, and the first holder unit 12 is inserted into a second holder unit 13 in order to maintain a constant gap between a magnet 11 disposed in the inner case 10 and a plurality of sensors 17 disposed in the second holder unit 13.
The magnet 11 in the first holder unit 12 is horizontally moved by a guide portion 14 which is formed in a lower portion of the inner case 10 and a guide groove 15 which is formed in a lower portion of the first holder unit 12. Also, the magnet 11 is vertically moved by the placement of a side surface of the first holder unit 12 on a plurality of rails 16 which are formed in a side surface of the second holder unit 13.
The conventional apparatus 20 for electronically controllable transmission can detect the position of the magnet 11 only in a particular direction and is an essential structure for sensing a constant magnetic field of the magnet 11. However, the installation of a plurality of holder units 12 and 13 is required to maintain a constant gap between the magnet 11 and the sensors 17. Accordingly, the increased number of such structures increases the size of a sensor unit, reduces layout utilization, and raises related costs.